After the rocker bumped into the jockey on holiday, the pair hit the margaritas and Liam admitted antics got “a bit f***ing silly”.
Frankie, 47, started bragging about his strong legs.
The singer said it happened while on holiday with The Prodigy star Liam Howlett, 47, who is his former brother-in-law, and another friend called Adam.
Gallagher said the trio were “sitting out drinking some margaritas” when Frankie walked over in his Speedos.
“Anyway, the tequilas are flying and all that tackle and it goes a bit f***ing silly.”
Asked about it, a spokesman for Frankie said: “It’s true. It was 10 years ago.”